Make RenderObject::style() return a const object

Source/core/rendering/RenderLayerModelObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010, 2012 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 73 matching lines @@
 
     RenderObject::willBeDestroyed();
 
     destroyLayer();
 }
 
 void RenderLayerModelObject::styleWillChange(StyleDifference diff, const RenderStyle& newStyle)
 {
     s_wasFloating = isFloating();
 
-    if (RenderStyle* oldStyle = style()) {
+    if (const RenderStyle* oldStyle = style()) {
         if (parent() && diff.needsPaintInvalidationLayer()) {
             if (oldStyle->hasAutoClip() != newStyle.hasAutoClip()
                 || oldStyle->clip() != newStyle.clip())
                 layer()->clipper().clearClipRectsIncludingDescendants();
         }
     }
 
     RenderObject::styleWillChange(diff, newStyle);
 }
 
@@ skipping 131 matching lines @@
             if (!rect.isEmpty()) {
                 rect.moveBy(additionalOffset);
                 rects.append(rect);
             }
         }
     }
 }
 
 } // namespace blink